Oil occurring in oil reservoirs is associated with varying quantities of water and gas. Both the water and the gas entering the well bore must be produced in order to produce the oil. In the early life of a field, when the reservoir pressure is high and wells are flowing, gas assists in lifting oil efficiently. However, in the later life of a field downwell separation of gas and oil becomes desirable when the well must be pumped.
If there is no separation of gas and oil before the fluid is pumped, the gas must go through the pump. When it does, it uses displacement that would otherwise be utilized for pumping liquid. In extreme situations, excessive quantities of gas cause the pump to "gas lock", and no fluid is displaced. For this reason, it has been found desirable to provide the downwell pump with a gas separator adapted to remove the gaseous substances from the well fluid being pumped to insure efficient and continuous operation of the downwell pump. If an ideal separation of gas and fluid is accomplished, all the gas flows up the annulus between the casing and tubing and enters the gas gathering system or flow line at the casing head. The de-gassed fluid enters the suction of the downwell pump and continues up the tubing, where it enters the production flow line at the well head. The gas separator of the present invention is intended primarily for use with reciprocating or jet type downwell pumps. The reciprocating pumps can be either the sucker rod type, which are powered by reciprocating the sucker rod string, or the hydraulic type, which are powered by high pressure power fluid operating a reciprocating engine and pump downhole. The jet pumps are powered by high pressure water or oil supplying power to a jet eduction system downhole. The invention would not be readily adaptable to a downwell centrifugal (also called a submersible or a submergible) pump since these pumps take their suction approximately in the center of the assembly and the multiple cup separator is for all practical purposes limited to pumps that take their suction at the lower end of the pump assembly.
Most prior art gas separators or anchors have ports in the side, and are more prone to draw in both gas and fluid. Some have had multiple cups, but have had no provision for two stage separation. Additionally, other gas separators are of a specialized design which must be placed between the electric motor, operating at the bottom of a submersible unit, and a centrifugal pump which is located at the top. An example of such a prior art gas separator is disclosed in U.S. Pat. No. 3,291,057, in the name of J. T. Carle. More particularly, the rotating shaft from the motor to the pump must pass through the center of the Carle gas separator. This shaft, together with other components, occupies a considerable amount of the cross section area which decreases the gas-liquid separation. Additionally, such a gas separator connot operate without a rotating source of power available to drive a charging pump and effect a second stage of separation. Accordingly, the art continues to seek improved gas separators which are more efficient and may be used with reciprocating or jet downwell pumps where there is no rotating source of power available to drive the pump and effect a second stage of separation.